Cardiac operations, such as angioplasty, stent deployment and ablation can be performed in a minimally invasive surgery (MIS) setting, by employing a catheter of the appropriate type. A surgeon, who performs a MIS, needs to observe the position and orientation of the tip of the catheter, continuously, in order to navigate the catheter to a desired location within the heart of the patient.
Methods and systems for determining the position and orientation of the tip of a catheter are known in the art. For example, such systems employ an electromagnetic sensor mounted at the tip of the catheter, and a medical positioning system (MPS), to determine the position and orientation of the tip of the catheter, according to an output of the electromagnetic sensor. The MPS determines the position of the tip of the catheter, within a vessel of the heart, where images are acquired by an invasive medical imager, from inside of the vessel.
One example of invasive medical imagers is an intravascular ultrasound (IVUS) imager, which is located at the tip of an IVUS catheter, to produce a plurality of images from inside the vessel. The IVUS imager employs an ultrasonic transducer at a tip of the IVUS catheter, to acquire the images. The IVUS catheter is inserted into the vessel, and advanced toward a region of interest within the body of the patient. The IVUS imager acquires a plurality of ultrasonic images during pull-back of the catheter from the region of interest, while the MPS detects the position of the tip of the IVUS catheter with respect to each of the ultrasonic images. A processor, which is connected with the IVUS imager and with the MPS, produces a video image of the inside of the vessel, according to the ultrasonic images, and the detected positions of the tip of the IVUS catheter. The IVUS catheter is employed in diagnosis and treatment of different diseases, such as atheroma, arteriosclerosis, and as an adjunct to balloon angioplasty and in guiding stent deployment.
U.S. Pat. No. 6,246,898 B1 issued to Vesely et al. and entitled “Method for Carrying out a Medical Procedure Using a Three-dimensional Tracking and Imaging System” is directed to a method for tracking the position and motion of a catheter, by employing a three-dimensional (3-D) tracking and imaging system. The 3-D tracking and imaging system includes a plurality of mobile transducers, a plurality of reference transducers, a computer system, an instrument, and an optional robotics subsystem. The computer system includes a 3-D tracking system, an imaging modality system, an image registration system, an image warping system and geometry transformation system, a user interface, and a display. The optional robotics subsystem includes a robotics control system and a robotic manipulator system. The instrument is a diagnostic tool such as a catheter. The robotics control subsystem controls the robotic manipulator system, which physically moves the instrument.
The mobile transducers are fitted onto the instrument. The reference transducers are mounted to locations on the patient in strategic reference locations. The imaging modality system acquires 4-D image data from a magnetic resonance imager (MRI). The position and movement of the instrument is tracked by the 3-D tracking system. The 3-D tracking system employs triangulation algorithms to determine the relative spatial coordinates of a combination of two transducers according to the time-of-flight principle of ultrasonic waves. The image registration system registers the position of the instrument with the corresponding spatial coordinates within the acquired images, provided by the imaging modality system. The image warping and geometry transformation system warps the image data to compensate for the changes that occurred in the period of time between image acquisition and surgery. The user interface enables user interaction with the computer system and the display displays the images provided by the image registration system.
An article by Jourdain, Mélissa et al. “3D Reconstruction of an IVUS Transducer Trajectory with a Single View Cineangiography.” Medical Imaging 2005: Image Processing, Proc. of SPIE 5747 (2005) is directed to a method for determining the three-dimensional trajectory of an IVUS transducer during an intervention by utilizing a single X-ray image and using a pullback distance of the ultrasound transducer as a priori information.
The method employs two imaging modalities, IVUS imaging and X-ray imaging. The IVUS imaging modality produces a sequence of cross-sectional images of a lumen within the body of a patient and the X-ray imaging modality produces a single-view X-ray image sequence. The method employs a single-plane model, a trajectory pruning technique and a tracking algorithm. The single-plane model utilizes a full perspective camera model and the knowledge of a pullback distance of a catheter inserted within a lumen of the body of a patient. The full perspective camera model is used as a basis for computing the projection of the position of the IVUS transducer in an X-ray plane. The trajectory pruning technique employs a cost function, and considers possible trajectories of the IVUS transducer on the X-ray plane. These possible trajectories are partly based on the curvature of the lumen. The cost function assigns specific weights to the solutions of possible trajectories based on the number of turns in the trajectory of the catheter.
The starting position of the IVUS transducer is inputted into the tracking algorithm. The tracking algorithm tracks the IVUS transducer by employing an image-differencing method (i.e., changes in pixel intensity) between consecutive frames in the image sequence. A 3-D position of the catheter is retrieved based on its previously-known position, outputted by the tracking algorithm, and with the known pullback distance of the catheter.
U.S. Pat. No. 5,724,978 issued to Tenhoff, entitled “Enhanced Accuracy of Three-dimensional Intraluminal Ultrasound (ILUS) Image Reconstruction” is directed to a method and apparatus for imaging an organ in a body of a patient, in order to obtain a three-dimensional image reconstruction from an acquired set of echographic data. The apparatus includes an ultrasound imaging catheter system and a catheter tracking system. The ultrasound imaging system employs a conventional intraluminal catheter with an imaging tip. The tracking system includes an ultrasound transducer. The ultrasound transducer is mounted adjacent to the imaging tip of the catheter. The imaging tip of the catheter acquires echographic images.
The catheter is inserted into the body of the patient and advanced into a required region of interest. The ultrasound transducer acquires an echographic data set (i.e., a sequence of 2-D images) within the region of interest during a pull-back procedure of the catheter. The tracking system tracks the position of the ultrasound transducer. The position of the ultrasound transducer with respect to each echographic data set at each point, during image acquisition along the pull-back path of the catheter, is calculated by determining a tangent to the catheter centerline of the ultrasound transducer, at each of the respective locations where the echographic data sets are acquired. The calculated position of the catheter is used to determine a three-dimensional pull-back trajectory of the catheter. The acquired sequence of the 2-D images is stacked in order to generate a 3-D reconstruction from the ultrasound images. Non-linear paths of the catheter are taken into account to avoid errors in the 3-D image reconstruction.
U.S. Pat. No. 6,148,095 issued to Prause et al., entitled “Apparatus and Method for Determining Three-dimensional Representations of Tortuous Vessels” is directed to an apparatus and a method for three-dimensional reconstructions of tortuous vessels employing IVUS and data fusion with biplane angiography. The apparatus includes a biplane angiographic unit, an IVUS imaging unit, a data fusion unit, and a display unit. The IVUS imaging unit includes a catheter. The data fusion unit includes a 3-D pullback path determination unit, a catheter twist determination unit, a correlation unit, an interpolation unit, and a phase correlation unit. The biplane angiographic unit and the IVUS imaging unit are connected to the data fusion unit. The display unit is connected to the data fusion unit.
The method includes the steps of initialization, image acquisition, centerline reconstruction, IVUS segmentation, data fusion and evaluation. The data fusion step includes the steps of catheter detection in 3-D, reconstruction of the 3-D pullback path, calculation of catheter twist, mapping, interpolation and rendering a quantitative analysis.
The biplane angiographic unit is calibrated in the initialization step. Image acquisition is performed by the biplane angiographic unit that acquires angiograms of the tortuous vessel, and the IVUS imaging unit that acquires IVUS images via catheter pullback from the tortuous vessel. The phase correlation unit uses the heart beat or the breathing cycle of the patient to ensure that the images acquired from the IVUS catheter are obtained under consistent conditions. The centerline of the vessel is reconstructed from a biplane angiogram. The acquired IVUS pullback images are then segmented. In the data fusion step, data fusion between biplane angiography and an IVUS pullback imaging is employed. Catheter detection in 3-D is performed using 3-D data derived from angiographic projection images. The 3-D pullback path determination unit determines a pullback path of the catheter from the acquired biplane angiograms, by employing a spline-based 3-D minimization approach.
The catheter twist determination unit determines a tortuosity-induced twist of the catheter. The correlation determination unit maps the captured IVUS image slices to the 3-D pullback path, according to a pullback speed and the determined tortuosity-induced twist. In the interpolation step, the centerline is approximated by Bezier curves. Borders between consecutive 2-D IVUS slices are interpolated and the IVUS slices are swept along Bezier-approximated vessel centerlines in order to generate the 3-D vessel reconstruction. The display unit displays quantitative representations of the IVUS images, angiograms and 3-D representations of the vessel.
US Patent Application Publication No. US 2006/0058647 A1 to Strommer et al., entitled “Method and System for Delivering a Medical Device to a Selected Position within a Lumen” is directed to a system and method employing graphically assisted medical positioning and imaging, for positioning a medical device within a lumen of the body of a patient.
The system includes a medical positioning system (MPS), an MPS catheter, two-dimensional image acquisition devices, a graphical user interface (GUI), and a processor. The catheter includes an MPS sensor at its tip. The processor is coupled with the GUI and with the MPS.
A stent which is to be deployed within the lumen is coupled with the catheter. An operator visually navigates the medical device by maneuvering it through the lumen toward a selected position. The position of the moving catheter within the lumen, as determined by the MPS, is associated with a three-dimensional coordinate system and is further associated with a respective activity state of an organ of the patient. IVUS images are acquired during the pull-back of the catheter from within the lumen. The lumen is externally imaged by a two-dimensional image acquisition device. The processor reconstructs three-dimensional images from the two-dimensional images acquired by the two-dimensional image acquisition device according to the organ timing signal of the organ. The trajectory of the catheter, detected by the MPS is superimposed on the three-dimensional images. The GUI displays a representation of the medical device on the three-dimensional image of the lumen.
An article by Slager, Cornelius J. et al. “True 3-Dimensional Reconstruction of Coronary Arteries in Patients by Fusion of Angiography and IVUS (ANGUS) and Its Quantitative Validation.” Circulation Journal of the American Heart Association 102 (2000): 511-516 is directed to a method for three-dimensional image reconstruction of coronary arteries by fusing angiographic and IVUS information. The method employs two imaging modalities: IVUS, which generates IVUS image cross sections and X-ray, which generates X-ray images. The method employs a motorized stepped pullback of a sheath-based catheter in order to acquire IVUS images, during an R-wave—triggered mode in a cardiac cycle. The method includes the steps of acquisition of a set of biplane angiographic (i.e., X-ray) images, acquisition of IVUS images, processing of X-ray and ultrasound images, 3-D reconstruction of a catheter centerline (i.e., coreline), and repositioning of the IVUS image cross sections on a reconstructed pullback trajectory. The method employs a wire model and a gutter model. Both the wire model and the gutter model estimate the length of the 3-D reconstructed catheter centerline.
The processing of the X-ray images includes the step of 3-D reconstruction of the catheter centerline and determining the borders of the lumen. The processing of the ultrasound images includes the step of determining the borders in the IVUS images, by employing a contour detection program. The 3-D reconstruction of the catheter centerline entails firstly, the direct 3-D reconstruction of the distal and proximal points of the centerline. Secondly, the centerline reconstruction between the distal and proximal points is approximated by employing a 3-D circular segment, which is adapted three dimensionally in a stepwise manner. The acquired set of biplane angiographic images record the 3-D position of the catheter and a 3-D pullback trajectory is consequently predicted.
Contours of the lumen obtained from the IVUS images are fused with the 3-D pullback trajectory of the catheter. Based on the reconstructed catheter centerline, the IVUS image cross sections are positioned on a reconstructed trajectory. The acquired IVUS image cross sections are distributed at equidistant intervals on the reconstructed catheter centerline and an angular rotation of the reconstructed IVUS image cross sections is determined. The reconstruction further entails the IVUS image cross sections to be angularly rotated around the 3-D pullback trajectory. The acquired biplane images are employed in optimization of the angular rotation of the reconstructed IVUS image cross sections. The pullback length which is determined according to the quantity of pullback steps is compared with the reconstructed path length, which is determined according to the wire model and the gutter model.